Electric percolator



p 9, 1952 E. KOLISCH 2,610,283

ELECTRIC PERCOLATOR Filed Sept. 28, 1949 3 Sheets-Sheet 2 |NVENTORATTORNEYS Sept. 9, 1952 E. KOLISCH 2,610,283

ELECTRIC PERCOLATOR Filed Sept. 28, 1949 3 Sheets-Sheet 3 INVENTOR Ema?!Kola'sch MM/ S MI/M MM ATTORNEYS Patented Sept. 9, 1952 ELECTRICPERCOLATOR Emil Kolisch, New York, N. Y., assignor to Continental Silver00., Inc., a corporation of New York Application September 28, 1949,Serial No. 118,354

3 Claims. 1

This invention relates to electric percolators, more particularly of thetype having automatic temperature control facilities including athermostat for cutting off percolation and thus determining the strengthof the coffee diffusion.

As conducive to a clear understanding of the invention, it is noted thatif the thermostat should reach its cut-off temperature before the coffeediffusion has attained the predetermined temperature corresponding tothe strength of coffee desired, the resulting diffusion would be tooweak, and on the other hand if the thermostat should not reach itscut-off temperature until after the coffee diffusion had attained suchpredetermined temperature, percolation would continue too long and theresultant diffusion would be too strong.

The rate of temperature rise of the thermostat of an electric percolatordue to radiation and convection from the heating element may varysubstantially in mass production from percolator to percolator becauseof the wide tolerance usually permitted in the rating of such heatingelement and also due to the tolerance in the distance between thethermostat and the heating element Within the percolator, so thatcorrespondingly wide divergencies result from unit to unit of any onemodel of percolator in the desired strength and temperature of thebeverage, unless costly and time-consuming special adjustment andregulation of each individual percolator is resorted to at the factoryin the attempt to compensate for such divergencies.

It is accordingly among the objects of the invention to provide anelectric percolator of simple, relatively inexpensive, compact andrugged construction, utilizing but few parts, substantially all of whichare conventional, in which the thermostat, though not exposed to contactwith the liquid will yet under all conditions of operation and withoutthe need for regulation of the percolator, reliably cut off percolationwhen the coffee diffusion reaches substantially the selected percolationcut-off that corresponds to the strength of coffee desired,substantially unaffected by tolerances in the heat output of the heatingelement, or by variations incurred in assembly in the relative positionof the heating element and the thermostat.

According to the invention, the percolator includes a control chamber insubstantially nonheat transfer relationto the electric heating elementbut having a relatively large heat radiating surface in heat conductiverelation '60 the liquid in the receptacle, and the thermostat con finedin said chamber is mounted in heat insulating relation with respect tothe electric heating element, so that said thermostat is sub-- jectedsubstantially only to the heating effect imparted thereto by radiationand convection of the air in the chamber which is heated substantiallyonly from the liquid in the receptacle which is in contact with saidheat radiating surface.

If an electric percolator is subject to unusual external temperatureinfluences, as for instance by exposure to draft in a cold environmentor by exposure to excessive heat, as for instance, in proximity to a hotstove, the operation of the thermostat therein may be seriouslydisturbed so that on the one hand cut-off will be greatly retarded orprevented entirely, or, on the other hand, will occur prematurely.

If an electric percolator were used at all times only under normalexternal conditions, such extraneous variations could be disregarded,but this might involve the need for precaution in use, and it isaccordingly another object to guard against the effect of unusualtemperature and movement of the external air, which might unduly disturbthe operation of the thermostat and thereby to avoid in all casespremature cut-off on the one hand before the desired strength of coifeehas been attained, or on the other hand, continuation of percolationlong after the coffee has reached such desired strength.

It is accordingly another feature of the invention to reduce so far aspractical, the transfer of heat by radiation between the control chamberand the external air, a result attained for practical purposes by liningthe externally exposed surface of the control chamber with insulationsuch as asbestos.

Another object is to provide an electric control sub-assembly forinstallation in a coffee percolator, which sub-assembly may readily bepreset so that when installed in any percolator of given construction itwill operate in substantially the same temperature range, regardless oftolerances in the output of the heating element thereof, of variationsin the positioning of the sub-assembly, or of fluctuations in thetemperature or movement of the external air.

In an electric percolator equipped with a thermostat set to cut offpercolation after the relatively short period of time required toproduce a relatively mild coffee diffusion of much less than maximumstrength, the temperature of the diffusion would, in general, be belowthe drinking temperature preferred by most persons and if, on the otherhand, the percolation is to stop only when the preferred drinkingtemperature has been attained, the diffusion would be stronger thandesired.

It is accordingly another object to provide an electricpercolator ,ofthe above vtypewhich, after operating initially as above set forth toeffect percolation of the liquid until the difiusion of coffee hasattained a predetermined tempera-.-.

lation ceases.

According to another feature of the invention,

.ancauxiliary thermostat controls the further application of heat .to.thecoffee diffusion, once'the previously. referred ,to .or mainthermostat has openedand the; percolation has ceased, said. auxiliarythermostat'maintainingthe diffusionwithin Qthe;dr.inl:ing temperaturerange that may be higher than the. temperature at which ,percola-.tiomceases formildcoflee orflower than the temperature at whichpercolation ceases for strong coffee, said auxiliary thermostat havingan associated .resistor which is the primary .source of thepost-perchlationheating.and which also serves to .maintain.themainthermostat open and thereby to,.pre.cludereepercolation.

In the,v embodiment hereinchosen .to illustrate theinvention, .a plate.of heat conductive material is desirably positioned .in the cavity ofthe. base cof the percolator .andaiiixed to the fioonof the receptacle,and extends across said cavity to. form the-control chamber, thatpart ofthe axial heating element, which extends into the cav'ity'being.at.theiexter ior of said .chamberand spaced from 'saidplate. V

.IJI'he .main thermostat which is positioned in asilch .control chamberis desirably mounted on said plate and thermally insulated therefrom andthe resistonor auxiliary .heating meansxwhich is .a'.lso.in said controlchamber is positioned in close heat transfer relation to .the .mainthermostat andto the floor of the receptacle. The resistor whichisinseries with theheating element is normally short circuitedbythemainthermostat and is, cut into circuit when the main thermostat isactuated, .thereby materially reducing the current, yet evolving,sufficient heat both to maintain the main thermostat-in open positionand to assure I .that the desired drinking temperature is maintained'.

"In the accompanying drawings in which are shown one or more of variouspossible embodiments, of the several ieatures-ofthe invention:

Fig, 11is a bottom-plan view of the percolator with;'the bottom plateremoved,

Fig.2 'is a fragmentary transverse sectional view'taken'along line 2-2of Fig. 1,

JE-ig. 3 isa viewflsimilar .to Fig. 1 on a larger scale showingthecontrol sub-assembly alone,

Fig. 4. is an elevational View of'the. control subassembly taken alongline 44' of Fig. 3,

Fig. 51s a diagrammatic"viewv of the control circuitand,

Figssfi and 7 are diagrammatic views ofthe control circuit in variousstages of operation.

Re'ferring now tothe drawings, there is shown apreferred embodimentofa-coffee percolator incorporating the temperature control sub-assembly.The percolator desirably comprises a receptacle i0 aiiixed to a hollowbase ii defining a cavity 12 therein. Screws M which pass through therim l5 of the base II and are threaded into openings (5 in the upturnedlugs 17 desirably tor-med integral with the periphery of the bottomzlate ,i 3. serve tosecure .theJatterinplace. Conlentional legs ig'ai'lixed to. the'bottorn plate space the percolator from the table.

Carried by the top E9 of the base i i, which deirably serves as thefloor of the receptacle, and ixtending through an opening 2K3 therein,is a heating element which includes a generally cylin-'drical,.preferablyceramic mount 2!. A cylindrical protective housing 22encompasses that portion of the mount which protrudes above top I9an'dalthou'gh itmay-be affixed to the latter in any suitable manner,illustratively has an inturned rim 23 extending under diametricallyopposed laterally extending ears 2.5 integral with the mount 2|. A nut25 secured upon the threaded lower end .26 .of .the. mount 25 whichprotrudes below top l9 into cavity 12, causes the ears 2G to be pressedagainst the inturned rim 23 of the housing 22 rigidly and securely to.clamp the housing 2.2 and mountJZl to'the base H.

.A resistance .wire 27 iswound around the upper vend28 '0f.the mountZ I,which desirably is of reduced diameter forming an annular ledge 29.Oneend 3! of the 'wireil' is desirably connected to the'.head ota'bolt32 which extends through a vertical bore 33 in ledge 29 and thelowerpor- ;tion of mount 2!, with the lower vend of bolt 32 protruding fromthe bottom of the mount as at '34, being. secured'in'place by 'a nut35.

The other end 36 of the resistance wire" 21 passesthrough a verticalbore 37! in ledge 29and the lower portion of. mount 2iv and. extendsfrom the bottom .of the mount as at38 and is connected as at 39 .to aterminal plug ll. Plug M is rigidly afiixed .to and insulated from theend wall 42 of .a socket 43 affixed to .the side wall 44 of the base Llas by rivets it over an opening 45 therein, as is .thecompanionterininal plug 35.

A conventional water ,pump 48 is .,provided, desirably, having a doubleWall well portion 49 witha small opening 5| therein and a tube 52 risingin saidreceptacle from said well 59 and mounting the conventional.cofiee basket (not shown).

The construction 'thusjfar described is not per se claimed. herein asitis conventional.

According to the present invention a control chamber 5.51s provided inthe base H to house controlequipment therein, and with .as.large .aheatradiating. surface as is practicably possible. Thecontrol chambermay be formed by positioning ,in .cavity 12,. a transverse ,partition.or plate .54 oraluminun alloyior other good heat conductive metal whichdivides the cavity I 2 into -.two chambers, i. e., the smaller segmentalchamber 58 and a larger segmental chamber 59, the heating element 27which is' axial or" top 59 extending atiitslower end 26 wholly in. saidlarger chamber. Plate5 3 desirably has its lateral edges 55 shaped tocorrespond to the conformation of "the inner lateral face of the wall ofthe base. so that when positioned in cavity l2 with the top edge 56thereof, as shown in Fig. 2, flush against the underiace of the top I9and at right angles 'thereto,the edges 55 will be but slightly spacedfrom'the inner face of the wall of the base and the plate will extend asa chord across the cavity LI The Width of the plate 54 is preferablysuch that the edge 51 thereof will be but slightly spaced from the plateI2.

By the spacing set forth the plate 54 is effectively heat insulated fromthe outer air and is subjected substantially solely to the heat of thepercolator content.

Means are provided securely to affix the plate 54 in cavit I2 so as toprovide for maximum heat transfer from the undersurface of top I9 toplate 54. Although plate 54 could be welded at its upper edge 56 to theadjacent top I9 of the base, in the embodiment herein shown, the plate54 desirably has a pair of ears 6| and 62 preferably formed integrallywith and extending laterally outward from said upper edge 56 intochamber 59 to lie flush against the undersurface' of top I9, to whichthey are afiixed preferably by rivets 63.

Chamber 56 is'preferab ly insulated from variations in the temperatureand movement of the external air by means of a thermal insulating shield66 desirably of asbestos, positioned against the arcuate wall portionthereof which is part of the wall of base I2.

A main thermostat 65 controls the percolation cut-off temperature and anauxiliary thermostat 66 is preferably also provided to control thedrinking temperature. While the mounting of the auxiliary thermostat 66is in no sense as critical as that of the main thermostat 65, it isdesirable for convenience and economy to mount it on the same support asthe main thermostat. More specifically the thermostats 65 and 66 aredesirably mounted on plate 54, one on each side thereof, with thermostat65 being positioned in chamber 56 and thermostat 66 being positioned inchamber 59. As these thermostats 65 and 66 may be substantiallyidentical, only the construction of one preferred embodiment ofthermostat 65 need be described; corresponding parts of thermostat 66having the same reference numerals primed.

Thermostate may comprise a bimetallic arm 61 carrying at its free end aninsulating stud 68 extending at right angles thereto and desirablytoward each other so that contacts I2 and I3 are normally in engagement.

Desirably one of said spring arms, illustratively arm 69, is of greaterlength than the other and protrudestherebeyond as at I4, such protrudingend 14 being in the path of movement of stud 68.

Associated with the spring arms 69 and H is a support arm I5 of rigidmaterial, on which an insulating stud I6 is adjustably mounted, with theend 11 thereof extending through an opening in spring arm 69 andnormally abutting against the face of spring arm I I.

The thermostats 65 and 66, each of which incorporates spacer washers 8|physically to separate its component elements and suitable insulatingwashers 66 electrically to insulate such elements, are mounted upon athreaded stud I9 which extends through an opening in plate 54 with oneof said thermostats on each side of the plate. By means of nuts 82 and83 threaded on opposed ends of stud 19 respectively, the thermostats aresecurely clamped together and retained on plate 54.

Desirably as shown in Figs. 1 and 3, a heat insulating washer 65 isprovided on stud I9 to insulate thermostat 65 from the heat which mightotherwise be conducted thereto from plate 54. Also heat insulatingwashers 65 and 66 are desirably provided on stud 19 to insulatethermostat 65 and thermostat 66 respectively from said stud, the end 61of which, as shown in Fig. l, is so near the lower end 26 of the heatingelement that it may readily be affected thereby. Accordingly thermostat65 is heated only from the walls of chamber 56 and this by radiation andconvection.

Stud I6 of thermostat 66 is desirably aiilxed to the end of a screw 66threaded in a suitable opening in arm 15 and slotted as at 69 to permitadjustment by means of a screw driver. Stud 16 of thermostat 65 isdesirably aifixed in the end of a rod 9| which has a fine pitch threadat one end for precise adjustment and is screwed into a nut .92 affixedto arm I5 and coaxial with an opening therein. The free end of rod 9Iextends through an opening 93 (Fig. l) in the side wall of the base Hand has a knob 94 afiixed to the protruding outer end thereof tofacilitate rotary adjustment. Rod 9I desirably has a collar 95 afiixedthereon by a set screw 96. Coil spring 96 encompassin rod 9| andcompressed between th nut 92 and the collar 95 holds rod SI and the stud16 controlled thereby in any position of adjustment.

In order to set the minimum and maximum range of thermostat 65 for mildand strong coffee respectively, nut 92 has an outstanding finger 99desirably formed integrally therewith which serves to limit the movementof stop I6I formed integrally with collar 95.

To connect the thermostats in circuit, the spring arms 69 and 'II havecontact lugs I63 and I64 respectively. Spring arm II of thermostat 65 isconnected by lead I65 affixed to lug I64 which extends through anopening I66 in plate 54, to terminal plug 46, and spring arm 69 isconnected by lead I61, aflixed-to lug I63, which extends through openingI66 in plate 54 to lug I63 of arm 69' of thermostat 66 and thence bylead I69 to the protruding end 34 of bolt 32 to which it is se cured bynut II I.

Resistor H2 is associated with thermostat 65 and positioned in chamber56 in close heat transfer relation to'thermostat 65 and also in closeheat transfer relation to the undersurface of the floor I9 of thereceptacle to heat the contents thereof in the manner hereinafterdescribed. Resistor I I2 is desirably tapped between the ends thereof asat II3 to form two sections 211 and H21), the former illustratively of300 ohms and the latter of 400 ohms.

Although resistor I I2 could be mounted in any suitable manner it ispreferably mounted on a substantially L-shaped supporting bar II4 ofelectrically conducting material, the horizontal leg I I! of whichextends, parallel to plate 54 through a bore in said resistor. The endof the vertical leg II5 of bar II4'is affixed to lug I63 by screw H6 andthe end of the horizontal leg III of bar H4 is connected by lead II6 toterminal I I9 at one end of resistor I I2. The intermediate terminal II3of the resistor is connected by lead I2I which extends through openingI22 in plate 54 to lug I64 of arm II of thermostat 66, and the otherterminal I26 of resistor I I2 is connected by lead I23 to lug I64 ofthermostat 65 to complate the circuit.

Thus as shown in Fig. 5, thermostat 65 is shunted across resistor H2,and is in series with the main heating element 21 with thermostat 66shunted across section Il2b of resistor II2.

amazes 7 2 the operationof the. percolator, rcoffee .cisi-put into-thebasket .and the .liquid'icontainer filled with water and 'closed' by asuitable cover. in familiarimanner'.. Knob 94-maythen'be turned to setthermostat 65 for mild, medium or'strong coff'eeas desired. 1 I

In one particular-model of percolato-rshown by way of illustration ashaving-a capacity of eight conventional cupsand incorporating a coldwater pump, the coifee diffusion to be mild would attain a temperatureof approximately 135 degrees F. which occurs after about minutes of.percolationand to be strongwould attain a temperature of approximately.l95-de'gr'ees F. which. occurs after about minutes of percolation,anyintermediate strength of coffee requiring a temperature and'period ofpercolation between the limits stated.- y

- With a :source of current appliedto: terminal posts, 4| and 46,heating element 2.! will be energized, the circuit being from terminal4i, lead 38, through heating element 27, bolt '32; lead I69 to lug I03of thermostat 66, lead lii'i-to .lug 1030f thermostat 65, through armI59 and normany-engaging contacts 12, 13, arm H, lug I04 and lead I65 toterminal 46. An alternative circuit is alsoprovided from lug. I93 ofthermostat 66, arm .69, contacts 12', 13,arm'7I', lug I04, through leadI2I to intermediate terminal H3 of heating element H 2, thencethroughsection H211 of said resistor H2, terminal I20 and lead I23 to arm I04to which lead I05 isconnected. As thermostat 65 effects ashor-t circuitacross resistor II2 substantially only heating element 21 which is oflow ohmic value, illustratively approximately '27 ohms, will limit thefiow of current through the circuit, and heating element 21, 'at'a linevoltage of'illustratively 110 volts, will produce approximately 448watts for heat-"Tlrius in a relatively short time the'waterwhichfentered well 49 through opening 5I,will

boil and as steam is generated it will lift the water up into tube 52 todischarge-in conventional manner'into the basketto startthepercolationaction.

However, as the water in the receptacle Iii is initially at thetemperature of tap water, usually approximately 60 degrees F., it willtake some time for the entire body of water therein to reach'th'edesired temperature. Consequently although the'percolation is going 'on,the top I9 oftheba'se I I, which serves-as the floor of the receptacleI0, as well as the plate 54 afiixed thereto will heat slowly havingsubstantially the same temperature as the contents of the receptacle.

Inthe heating operation, while the lower end of the main heating element21 including the ceramic mount thereof and the exposed metalconnections'may become hot, this heat has no "material efiect on thetemperatur of the air 'withinthe control chamber 58, because thepartion' 54 serves 'as a barrier substantially to preelude transfer ofheat to such chamber byradiation or convection from such heatingelement.

'.for heat from the base of the heating element to thenmain thermostat65, because its mounting stud 1 9. is effectively heat insulated,fromthe heating element by the various 'heatinsulating washers 84, and86. b y

.-By reasonof the relatively large metalradiating surface of the controlchamber 58 directly heated from the liquid in the receptacle, the airand thermostat within the control chamber will follow closelyintemperature that of said liquid, especiallyas the loss of heat from saidcontrol chamber is minimized by the heat insulating liner 60 on theexposed surface thereof. In the particularmodel of-percolator heredescribed, a temperature diflerential of approximately 10-degrees F. mayreadily be maintained between the liquid; in the receptacle and thethermostat throughout the operative range between mild coffee and strongcofiee percolation cut-off temperature.

Thus by originally setting the main thermostat 55 to open at atemperature lower thanthat of the temperature of coffee of the desiredstrength by such substantially fixed differential maintained between thetemperature of the liquid in the receptacle andthe air in the con.- trolchamber, the thermostat will accurately control the temperature ofpercolation cut-oifto the desired value. 7

Reliability of the percolator under normal operating conditions is thussubstantially assured and the percolation will be cutoff atsubstantially exactly the temperature corresponding to the strength ofcoifee desired.

Even under adverse conditions of operation encountered in use of thedevice, no material variation will occur, in the temperature or strengthof the coffee produced. Thus, for instance, in using the percolator invery cold and drafty environment, although there may be somewhat moreheat radiation from the control chamben-despiteits heat insulating liner60, the relatively large radiating surface of the control chamberexposed tothe heat of the liquid in the receptacle will speedily conductsuch heat to maintain the air in the chamber at substantially thetemperature differential desired with respectto the liquid withoutmaterial variation and hence the opening of the main thermostat is notretarded, so that the coffee will not be stronger than desired. And onthe other hand when the percolator is used in a very hot environment theheat insulating liner :60 will minimize the transfer of heat into thecontrol chamber 58, so that the temperature differentialwith respect tothe liquid will be maintained substantially constant, and hence the mainthermostat willnot open prematurely so that the coifee'will not beweaker than desired.

If the thermostat 65 is set, for example, to m-akemild coffee, when thetemperature in chamber '58 reaches approximately 125. degrees F.,thermostat 65 which had'been set to operate at this temperature, wouldopen. ,W ith thermostat 65 thus open, the circuit would be a's'shown inFig. 6A,.and the short circuit about resist-or H2 would thus be removed.However, as the auxiliaryIthermost-at 66 still remainsclosed as it ispre-set-to operate :when the "contents of the receptacle are at theoptimum drinking temperature at which the temperature in chamber 59would be approximately between degrees and -degrees F., only-sectionII2a of resistor IIZ would "be in circuit, Section I I Zabeing in serieswith resistance wire 2'I,the current in the heating circuit ismaterially reduced as is the heat produced thereby. For example, withsection IIZa, illustratively of 300 ohms, in series with acidosisresistor wire 21, illustratively of 27 ohms, the heat ,produced byresistance wire 21 would only be 2.94 watts and the heat produced bysection I I2a and I I2b of resistor liz nowin series with resist- .ancewire 21, the current in the series circuit will be materially reducedand only .62 watt will be produced by resistance wire 21 and 15.96 wattswill be produced by the entire length of resistor IIZ. Although 15.96watts is suflicient'to keep thermostat 65 open, it is not sufficient tomaintain the temperature of the contents of the receptacle at150 degreesF. and hence such temperature, as well as the temperature of chamber 59will start to drop until the temperature of the coifee drops to 145degrees F. At this time thermostat 66 will re-close and resume theposition shown in Fig. 6A and the heat produced by resistor II2 willagain increase.

' Thus in operation, mild coffee is brewed by stopping percolation whenthe receptacle contents are at a temperature, illustratively 135 degreesR, which is below a desirable drinking temperature, but continuingheating the c-oiree without percolation untiltlie desired drinkingtemperature, illustratively approximately 150 degrees is attained.

When strong coffee is desired, thermostat 65 is set toopen whenthecofiee diffusion has reached illustratively the temperature of 195degrees F. Thermostat 66 will open at 150 degrees F., that is, beforepercolation has topped. At that time the circuit connections are asshown 'in Fig. 7A. As thermostat 65 is still closed and shunts resistorI I2, the opening of thermostat 66 will have no effect. a

When the temperature of the diffusion has reached 195 degrees F.,thermostat 65 will open to cut resistor II2 into circuit, the circuitbeing shown in Fig. 7B. As only 1596 watts is being produced by resistorH2 at this time, which although suflicient to keep thermostat 65 open isnot sufiicient to maintain the temperature of the coifee diffusion, suchlatter temperature will fall until it reaches the desired drinkingtemperature of approximately 145 degrees F. at which time thermostat 66will close as shown in Fig. 70 to short circuit section Il2b so that theheat produced by section I I2a will increase to 3267 watts again toraise the temperature of the diffusion.

For medium coffee percolated to a temperature of, say, 150 degrees F.,and taking approximately minutes of percolation, the knob 94 will be setto intermediate position and the operation and automatic control will bereadily understood from the above description.

Once the main thermostat 65 has been actuated, by reason of the closeproximity thereto of the hot resistor II2, it will remain openregardless of changes in the ambient temperature; and as long asthermostat 65 is thus kept open, the current flowing through the circuitwill be so reduced that the heat produced by the main heating element 21will not be suflicient to cause resumption of percolation, so that oncecofie'e of the desired strength has been brewed, the possibility ofre-percolation, which would make the coffee too strong, is precluded.

By means of the auxiliary thermostat 66, a drinker of mild cofiee whichgenerally is percolated to a temperature too low to be palatable,obtains such mild coffee at the desired drinking temperature. Yet thisauxiliary thermostat does not detract from the desired operation withstrong coifee that is generally percolated to a temperature too hot forthe ordinary consumer and serves to bring such coffee down to andmaintain it at desired drinking temperature.

As the device is automatic in operation there is no need for the user totime the same or keep watch thereover. All that is required is to plugin the unit and turn the adyustment knob 94 Ior the desired strength orconee.

When the circuit is opened, resistor II2 cools and thermostats lip andBo reciose so that the unitis automatically re-set to the conditionshown in 111g. 5 preparatory for the next use.

1t 15 distinctly to D8 understood that the numerical values or ohmicresistances and resultant wattages, the periods or time, thetemperatures and temperature oiri'erentials and in fact all othernumerical values here mabovestated are illustrative merely and would. bepredetermined .Ior each model OI percolator made according'to thepresentinvention and the component parts but all percolators oi'ahy one modelas fabrieaten and assembled in mass production, will performsubstantially uniformly in the manner desired, substantially regardlessof the tolerances in the heater and in the positioning of the controlunit and the like, and this without the need for adjustment orregulation.

The thermostats incidentally function as safety devices to preventdestruction of the heating element 21,'the resistor Ill and thepercolator itself, in the event the circuit is closed with insufiicientor no liquid in the receptacle. In that event the temperature of thereceptacle would quickly rise to over 195 degrees F. (assuming it is setto operate at this temperature) and thermostat 65 will open, greatlyreducing the current by placing resistor I 12 in series with the mainheating element 21 and thermostat 66 will thereupon function to keep thereceptacle at the safe temperature of below degrees F.

As many changes could be made in the above construction and method, andmany apparently widely different embodiments of this invention could bemade without departing from the scope of the claims, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In an electric percolator of the type comprising a receptacle havinga floor, a base for said receptacle having a cavity therein, an electriccircuit including a heating element for said receptacle; the combinationtherewith of a sub- 11 I stanti'ally upright partition of heatconductive material extending across-said cavity and'affixed to'thefloor of said receptaclesoas to conduct heat from the contents thereof,said partition defining a control chamber'within said cavity exteriorlyof said heating element, said partition serving substantially to bartransfer of heat by radiation, by conduction and by convection, fromsaid heating element to said control chamber, said control chamberhaving a, wall exposed to "the exterior of the percolator, heatinsulation means associated with said wall to impede the transfer ofheat with'respect to said control chambena heat responsive switch insaid control chamber connected to control'the operation of "saidheating-element, a heat insulating mount '1for'said,switch,'a resistorin said control chamber in close heat transfer relation to the floor of"said receptacle and to saidswitch and normally shunted by the' latterwhereby upon opening'of said receptacle having'a cavity therein, andanelectric'circuit including a heating element for saidreceptacle; thecombinationtherewith ofa substantially upright partition of heat conduc--tivematerial extending across said cavity and "aflixed to the floorofsaid receptacle and depend- 'ing'therefrom was to conduct heatfrom thereceptacle contents, said partition-defining a controlcham-ber withinsaid cavity exteriorly of said heatingelement, said partitionservingsubstantially to-bar transfer of'heat by radiation, by conduction-and byconvection from said heating'ele- 'ment to said controlchamber, a heatresponsive switch in said control chamber, a resistor in said 'controlchamber in series with said heating elementand in-close heat transferrelation to the floor of said receptacle and to said switch and normallyshunted by the-latter, a second heatresponsive switch in said cavityexteriorly of said control chamber and normally shunted across a portionof said resistor, means extending through said partition andmountingsaid switch on each sidethereof-respectively, and means'heat insulatingsaidfirst named switch from-said mount'and from-said heatingelement.

3. A temperature control circuit to control the operation of an electricpercolator of the type having a heating element, said control circuitcomprising a resistor in serieswith said heating element, a normallyclosed thermostat shunted across said resistor and responsive to thetemperature of the receptacle contents, means for adjusting at will thesetting of said thermostat whereby said thermostat will open at aselected temperature to remove the shunt across said resistor and reducethe current through said heating element to stop percolation, a normallyclosed thermostat shunted across a portion of said-resistor andresponsive to a predetermined desired drinking temperature of thereceptacle contents whereby upon opening of said first named thermostatthe heat evolved by said resistor'will increase the temperature of thereceptacle contents to the drinking temperature range, and upon openingotboth of said thermostats the temperature of the receptacle contentswill decrease to the drinking temperature range, said second namedthermostat being set intermittently to open and close to maintain thetemperature of the receptacle contents within a desired drinkingtemperature range.

EMIL KOLISCH.

- REFERENCES CITED The following references are of record in. the fileof this patent:

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Kolisch Oct. 17, 1950

